Ionic crystal relay system



y 12, 1955 P. RAIBOURN 2,713,116

IONIC CRYSTAL RELAY SYSTEM Filed July 8, 1950 CONTROL SIGNAL SOURCE VOLTAGE SOURCE SIGNAL SOURCE INVENTOR Paul PQLE' ourn:

ATTO RN EY5 IQNZC CRYSTAL RELAY SYSTEM haul Raibourn, Southport, Conn.

Appiication July 8, 1950, Serial No. 172,761

4 Claims. (Cl. 250-7) This invention relates to a pickup device for use in communication systems and particularly to pickup devices for use in transmitting radio programs or television scenes to a central broadcasting station where they are to be rebroadcast. The device is useful in a relay system for picking up a program originating at one point and relaying it to another. The device is also useful in systems carrying telephone and telegraph messages, for picture transmission or simply for direct communication.

A fundamental aspect of the invention embodying the device is that the signal to be transmitted is carried upon a visible or invisible light beam which will have impressed thereon a wide band of modulation, so that a television program, or many individual audio programs, may be transmitted on a single beam. In this connection the invention is very useful in that it provides means for putting together a relay system which is economical, efiicient and faithful in the reproduction of the transmitted signal.

The invention, accordingly, involves a system embodying the use of ionic crystals in a relay tube which crystals have the property of becoming opaque to light of certain wave lengths if their theoretically uniform crystalline structure and accompanying interionic electrical fields are disturbed by the presence of electrons in certain positions other than electron orbits normal to the theoretically uniform crystalline structure. This condition of strain can be increased or caused by bombardment of the ionic crystal surfaces with X-rays, ultraviolet rays, cathode rays, electron streams, certain positive ions, or any other similar radiation phenomenon which aids the escape or capture, of electrons by ions in the crystal. The electrons thus producing the absorption band can be moved within the crystal by the application thereto of electric fields or electrical potentials and it is this feature of the ionic crystals which is embodied in my preferred form of invention.

My invention accordingly comprises an ionic crystal signal relay system and tube including a grid covering the faces of the said ionic crystal to which electric potentials are applied to restore the electrons to their orbits at a frequency corresponding to the modulation signals received, which system thus incorporates the features of construction and combinations of elements and arrangement of parts hereinafter to be described in greater detail.

Of the ionic crystals which can be used in scanning tubes, either a single crystal or a large number of crystals coated on a surface can serve the functions desired. The essential feature is to provide a large area to be irradiated in the ionic crystal tube. It is known that these crystals are normally transparent to visible light and that when they are struck by a beam of radiation, such as the several types mentioned, opaque material, which will be hereinafter identified as opacity centers, is created in the crystal and the degree of opacity will be proportional to the intensity of the incident radiation.

2,713,115 Patented July 12, 1955 Of the various types of ionic crystals which can be used the alkali and alkaline earth halides, which are characterized by having a simple cubical crystal structure, are particularly sensitive to these effects and their absorption bands are found largely in the region of the visible light and near infrared. Accordingly, their utility for transmission of signals on visible light beams and infrared light beams by modulation thereof is apparent. Specifically, sodium, potassium, lithium, calcium, barium and strontium chlorides, bromides, iodides and fluorides are useful.

Detailed information on such crystals, their properties and the nature of the opacity centers is found in the book Electron Processes in Ionic Crystals by N. W. Mott and R. W. Gurney, published by the OX- ford University Press in 1940. Such ionic crystals are also described in United States Patent 2,330,171, issued September 21, 1943, to A. H. Rosenthal, and in the Proceedings of l. R. B, May 1940, pages 203 to 212.

The invention can be understood more clearly in its various details by reference to the accompanying drawing in which,

Figure l is a diagrammatic representation of an ionic crystal signal system arranged in accordance with the instant invention; and

Figure 2 is a representation of a typical circuit which would be used in the system to restore the crystals to transparency.

In Figure l a diagrammatic representation of the signal relay system embodying the improvement in restoring the transparent ionic crystal is shown. There, 10 represents a source of light which is located at the focal point of parabolic reflector 11 from which the beam 12 is represented as being reflected to ionic crystal tube 13 in which 14 represents the ionic crystal surface on which the beam impinges. The crystal is heated electrically to the desired operating temperature by connection through leads 15. The modulated beam 12 emerges from the back of the tube 13, grids 16 and 17 substantially screen the face of the ionic crystal and have restoring voltages applied thereto through line 18 from source 19. The electrical modulating signal is applied to the electron gun structure 35 within the tube from a source 20 of signals. The cathode ray beam is generated within the gun 35, is modulated by the signal from source 28 and directed to irradiate substantially the entire face of ionic crystal 14.

In Figure 2 there is shown a typical circuit for the application to the grids 16 and 17 of appropriate restoring voltages. Thus the block labeled Signal Source (which could be the modulating signal source 20) supplies voltage pulses varying with the modulation signals applied to the cathode ray beam of the tube, which voltages are coupled through capacitor 21 and RC circuit 22, 23, in which the capacitor is variable, to the grid 24 of the tube 25. The restoring voltage source is also coupled through capacitor 26, resistor 27 to the cathode 28 of the tube, which in turn is coupled through capacitor 29 and resistor 30, to the high voltage supply. Screen grid 31 of the tube is also connected to the high voltage supply. The signals obtained from the tube are taken from the plate 32 and connected to coil 33, which in turn is connected through resistor 34 to the high voltage supply.

The signals thus generated by the source of pulses are applied from the coil 33, through terminal 36, to the grids 16 and 17 Where they operate at a rate depending upon the modulating signal with an intensity related to the modulating signal to restore the crystal 14 to transparency. The crystal is heated electrically to operating temperature through leads 15, and the additional heat effect needed to restore the crystal to transparency after development of opacity through the modulation of the cathode ray beam is supplied by grids 16 and.17.

Thus, though the invention has been described as only a single embodiment, the basic principle thereof, which involves the application to an ionic crystal through appropriately placed grids of a restoring signal varying with the modulating signal, thereby to condition the crystal for additional modulation of incident light, the crystal receiving ever substantially all its area the modulating radiation, through the varying corrective voltage, it should be clear that variations thereof in the details of the arrangement of parts in the apparatus can be made without departing from the spirit or scope of the invention.

This application is related to my application Serial No. 523,683, which is now Patent No. 1,515,263 issued July 18, 1950 and in so far as it discloses new matter is a continuation in part thereof.

What is claimed is:

1. An electron ray tube havingtherein an ionic crystal, means for impressing a signal modulated beam of electrons simultaneously upon a large portion of the entire area of said ionic crystal, means for projecting a beam of light upon said ionic crystal, and means meeting said source to said grid, said signals applied to said grid providing an electric field over said screen for restoring said crystals.

4. An electrical signal system comprising an electron tube having an ionic crystal screen, a gun structure for generating and directing a dispersed beam of electrons toward said screen to impinge simultaneously upon substantially the entire surface thereof, and an electron perforate electrode positioned in the path of said beam and adjacent said screen to cover substana tially the entire area thereof, a source of input signals connected to said gun structure to modulate said beam and a source of control signals connected to said electrode and to said source of input signals thereby to apply signals to said electrode corresponding to and a varying with said input signals and providing a restoring electric field across said crystal screen.

Levy et al. Dec. 12, 1950 Skellett Dec. 26, 1950 

